The present invention is relating to an integrated circuit package, particularly to a BGA package having a plurality of circuit boards.
An integrated circuit package with a window BGA packaging type (window Ball Grid Array package) is disclosed in U.S. Pat. No. 6,049,129 xe2x80x9cchip size integrated circuit packagexe2x80x9d. FIG. 8 is a cross-sectional view of the integrated circuit package 30 and FIG. 9 is a top view of the integrated circuit package 30. The integrated circuit package 30 comprises a silicon chip 50 having integrated circuit elements. The silicon chip 50 is attached onto a multi-layer printed circuit board 70 by an adhesive layer 60. The multi-layer printed circuit board 70 has a plurality of routing strips 82 and corresponding conductive pads 10, the pad 10 formed on the first surface 92 of printed circuit board 70 is bonded with solder ball 15. An opening 86 is formed at the center area of the printed circuit board 70 for exposing the bonding pads 12 of silicon chip 50 to enable metal bonding wires 80 to pass through and electrically connect bonding pads 12 of chip 50 with routing strips 82 of printed circuit board 70. The potting material 90 can be formed only by potting method because it is divided into two isolated portions around the perimeter of chip 50 and within the opening 86 (blocked by chip 50), however a special mode with multi-injection is required in case of forming the potting material 90 by molding method. Besides, thermal stress of chip 50 and printed circuit board 70 caused by different coefficients of thermal expansion (CTE) results in the deformation of the integrated circuit package 30.
The main object of the present invention is to provide a multi-board BGA package that has a plurality of circuit boards formed on a same plane to hold at least a chip so as to reduce thermal stress caused by CTE mismatch.
The secondary object of the present invention is to provide a multi-board BGA package that comprises a plurality of circuit boards. A galley formed between adjacent circuit boards for passing through the metal bonding wires to connect chip with circuit boards, and also the package body is easy to be filled during molding process, besides a flexible space is provided for avoiding warping and having better elasticity.
The multi-board BGA package according to the present invention comprises:
a plurality of circuit boards, each circuit board having a first surface and a second surface, wherein the first surfaces of the plurality of circuit boards are formed on a same plane, and a galley is formed between adjacent circuit boards;
at least a chip adhered on the second surfaces of circuit boards, the chip having a plurality of bonding pads;
a plurality of metal bonding wires passing through the foregoing galley and connecting bonding pads of the chip and the circuit boards;
an encapsulant body formed in the galley and on the second surfaces of circuit boards; and
a plurality of solder balls bonds on the first surfaces of circuit boards.